They also point out that avians may be the victims of an "inflated system of organismal classification". (We tend to think of species that can hybridize as being in the same genera.)

Actually, whether or not these populations are actual species yet in the strict sense of the term is irrelevant. The fact remains they are morphologically and ecologically distinct, and reproductively isolated, which can only lead to further divergence. In other words, they are species in all but complete post-zygotic isolation.

Ducks and geese are separate species, even if they can hybridize on occasion. There's no significant gene flow between the populations and consequently they keep their distinctive characteristics. Classification inflation refers to the numbers of higher level taxonomic categories when compared to other vertebrate classes. Of course, the only guide here is consistency—where we cut the phylogenetic tree is arbitrary.

I was thinking more of the IDers perspective on this and evolutiionary theory. Diversity depends on isolation and divergence. And that's what we see, regardless of the taxonomic headaches.

--------------Those who know the truth are not equal to those who love it-- Confucius